The fashion conscious women of Roman Britain used a tin-based foundation to get a pale and appealing look.

The evidence comes from a sealed pot of ointment found at an archaeological dig in Southwark, south London, last year.

Bristol University scientists analysed the cream and found it to be made from animal fat, starch and tin oxide.

They tell Nature magazine that their own version of this second century AD cosmetic leaves a smooth, powdery texture when rubbed into the skin.

I remember when the jar was opened I took a sharp step backwards

Francis Grew, Museum of London

The plainly decorated pot was an extraordinary find. Just six cm across and five cm high, it was discovered in a drain at the site of a temple complex now known as Tabard Square.

Marks left by the last fingers to use the cream pot were still visible on the lid.

Modern counterpart

At first, guesses as to the cream's use included a cosmetic purpose, a possible toothpaste, a barrier cream and even something ritualistic that was smeared on goats before they were killed.

But the Bristol researchers are pretty sure the cosmetic explanation is the best.

The marble plaque was found at the junction of three key Roman roads (Image: PreConstruct Archaeology)

"It's got this tin-oxide component which looks like it is a pigment - it's an inert material and when you rub it on your skin it goes white," biogeochemist Professor Richard Evershed told BBC News.

"We can't find any indications in the literature for medicinal properties - especially for an inorganic tin like this."

The team synthesised its own version of the cream made to the same recipe. When they rubbed it into their skin, the fat melted to leave a residue with a smooth powdery texture.

This quality was created by the starch - still used for this purpose in modern cosmetics.

Big stink

"I think probably we are dealing with quite a sophisticated thing," said Francis Grew, curator of archaeology at the Museum of London and a co-author on the Nature report.

"We do know from historical references that upper-class women in particular apparently spent ages dealing with their make-up, with their cosmetics."

It is known that white face paint was fashionable in Roman times and this colour would normally have been derived from lead acetate. But for Romans exploiting British mineral resources, the tin would have been a more than acceptable substitute.

The fact that the pot had survived nearly 2,000 years intact with the lid tightly sealed made the researchers' work a good deal easier.

"I remember when the jar was opened I took a sharp step backwards. The smell was strong and pungent; it smelt of rotten eggs," Grew recalled.

London's name

Professor Evershed added: "It does start to intrigue you - the knowledge that they had of the properties of the materials that they were selecting.

"They weren't choosing materials by accident. They probably had years of observation and experimentation, mixing materials together to alter their properties."

The 1.2 hectare Tabard Square dig revealed the remains of two square, Romano-Celtic temples and a large piazza. It is rare evidence of organised religion in London 2,000 years ago.

Its other major discovery was a white marble inscription with a dedication to the god Mars Camulos. The relic refers to "Londiniensium", meaning "of the people of Londinium".

This is the earliest known reference to London's Roman name.

The Tabard Square site is being covered over by a large residential housing, retail and leisure complex.